الفهرس 
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Abstract
The aim of this study was to produce instant soluble powders, having high phytochemical and color characteristics, prepared from hot air foam-mat dried (FMD) strawberry and/or tomato. Two types of foaming agents were used in this study; freeze-dried egg white (EW) and spray-dried soy protein isolate (SPI), at different concentrations. A central composite rotatable design of experiments was defined with two parameters (concentration of foaming agent and whipping time) with 5 levels for each parameter. For strawberry, the concentration of foaming agent varied from 0.5 to 9.0% and the whipping time from 1 to 8 min. However in case of tomato, the foaming agent concentration varied from 1 to 5% and the whipping time from 2 to 14 min. The foam was prepared by mixing the puree of strawberry or tomato with the respective concentration of foaming agent and whipped for the respective time, according the experimental design. The foam was then dried in a thin layer (4 mm ±1) at 50°C. A 4±1 mm thick dried control sample at 50°C was used for a comparison. The effect of foaming agent type and foaming parameters on the foam characteristics and on the different quality attributes of powder was studied. The obtained results showed that the hot air-foam-mat dried powders had superior quality than the powder obtained by Convenentional hot dir drying, except the flow properties. Besides, the concentration of foaming agent was the predominant parameters affecting the studied responses which were dependent on the type of foaming agent. The foam characteristics were better when EW used as a foaming agent compared to SPI. Although that, the powder prepared with SPI had higher sensorial and phytochemical properties and better color characteristics than the powder prepared with EW. For foaming conditions of 9% as a concentration of foaming agent and 4.5 min as a whipping time, the total phenolic and flavonoid content of strawberry powder, prepared with EW, increased by about 18% and 53%, respectively, compared to the control sample. While, these responses increased by about 21% and 64%, respectively when SPI used as a foaming agent. Comparing the two types of foaming agents, the total phenolic and flavonoid content of strawberry powder, prepared with SPI, increased by about 3% and 7%, respectively, compared to the powder prepared with EW. Similarly, the antioxidant activity for the same conditions increased by about 247% and 258%, respectively, in strawberry powder prepared with EW and SPI compared to the control sample. On the other hand, an increase by about 60% and 33% was observed in total phenolic and flavonoid content for tomato powder prepared with EW under foaming conditions of 5% as a concentration of foaming agent and 8 min of whipping, compared to the control sample. These responses increased by about 97% and 39%, respectively, when SPI used as a foaming agent under the same conditions. Comparing the two types of foaming agents, the SPI caused an increase by about 23% and 5%, respectively, in the total phenolic and flavonoid content, compared to EW. The antioxidant activity increased by about 57% and 63%, respectively for tomato powder prepared with EW and SPI compared to the control sample. The strawberry and tomato powders prepared with EW and SPI were red in color with higher color saturation than the powder obtained by conventional hot-air drying. Hot air-foam-mat drying improved the solubility of strawberry and tomato powders. The insolubility index of strawberry powder, prepared with EW and SPI under foaming conditions of 9% and 4.5 min, decreased by about 39% and 31%, respectively, compared to the control sample. Similarly, the insolubility index of tomato powder, prepared with EW and SPI under foaming conditions of 5% and 8 min, deceased by about 46% and 31%, respectively, compared to the control sample. This study stated the promising use of soy protein isolate as a foaming agent due to its role in increasing the content of bioactive compounds and antioxidant activity of strawberry and tomato powders. Therefore, the hot air-FMD strawberry powder could be used as a functional food in the preparation of different food formulations such as bakery products, beverages, and ice creams. Similarly, the hot air-FMD tomato powder could be used a functional food in many food formulations and dishes such as tomato soup and cooked dishes.